Effects of pyrolysis conditions on gas separation properties of 6FDA/DETDA:DABA(3:2) derived carbon molecular sieve membranes

Abstract

A previously reported polyimide, 6FDA/DETDA:DABA(3:2), was pyrolyzed under different protocols to produce carbon molecular sieve (CMS) dense film membranes for separation of important gas pairs, including pure gases CO 2 /CH 4 , O 2 /N 2 and mixture gases 50% CO 2 /50% CH 4 and 50% C 3 H 6 /50% C 3 H 8. This study investigated the effects of pyrolysis temperature, O 2 doping, and precrosslinking on the separation performance of 6FDA/DETDA:DABA(3:2) CMS membranes. Comparing to the precursor membranes, separation performance of all 6FDA/DETDA:DABA(3:2) CMS membranes improves significantly with both higher permeability and selectivity. The CMS film pyrolyzed with a novel method, i.e., 800 o C with precrosslinking, shows very attractive separation performance with CO 2 and O 2 permeability of 4678 Barrer and 683 Barrer, CO 2 /CH 4 , O 2 /N 2 selectivity of 71.5 and 8.0. Sorption measurements provide insight into the pore size distributions among these CMS membranes. The effects of these three parameters during pyrolysis on the CMS membranes gas separation performance are

Carbon molecular sieve structure development and membrane performance relationships

“…1 and 7 (45). Another study demonstrated that for different 6FDA-based polyimide precursors the same effect applies, and presumably is general to all CMS materials (46). While determination of the exact state of the oxygen is outside the scope of this current discussion, spectroscopic evidence of carbonyls has been previously reported (43); however one can envision a multitude of oxygen chemisorption pathways during the complex pyrolysis process.…”

A simple one‐step drop‐coating approach on fabrication of supported carbon molecular sieve membranes with high gas separation performance

“…It suggests that the microstructure of CMSMs turns to more compact with increasing the pyrolysis temperature. This agrees well with the law in reports . By this means, the microstructure and gas permeability of resultant CMSMs can be tailored by pyrolysis temperature.…”

Effects of Diatomaceous Earth Addition on the Microstructure and Gas Permeation of Carbon Molecular Sieving Membranes

“…During the third stage, a large amount of small molecular gases would be released, such as H 2 , CO, CO 2 , O 2 , CH 4 , and NO X , resulting into the formation and evolution of the porous structure in membrane substrate ,. When the pyrolysis temperature goes up to 650 °C, the TG curves become placid because of the alternation of predominantly thermal reaction from decomposition to poly(condensation) . The slight weight loss of precursor at the temperature above 650 °C is due to the successively rearrangement and reorganization of the remaining membrane matrix.…”